Would you use the same moisture content schedule to dry random width & length 8/4 walnut as you would dimension stock?
8" x 16" x 2 3/8". I get very little h/c in a 30,000' charge of 8/4 but will see 5 to 6% h/c in a charge of 35,000 pieces of the dimension. The dimension pieces are defect free, waxed on both ends, and have sticks every 5".
Short dimension pieces have more surface to volume, so they dry faster, which means more risk. Also, Dimension can have a defect an inch or two from the end, but this defect was cut off. Overall, this means cross grain at the end of a dimension piece, which again is more defect prone.
Thanks for your input. I forgot to mention that in both cases I am talking about walnut.
As said, the higher the relative surface area, the more forgiving the kiln schedule must be, especially if starting higher than the fiber saturation point. I don't go as conservative as a 4/4 schedule, but certainly dial it back a little whenever I'm drying small chunks, especially high value walnut. I will also run cooler temperatures, and try to get to the characteristic "walnut stall" point, then I increase the temps, and then finally drop the wet bulb.
I assume you are using a steam kiln?
Yes steam kilns. These charges are pretty green. Usually start in the 70 to 80% moisture range. I start with a 4 degree depression and stay a step behind where 8/4 would be for any given moisture content. These are mostly all plain sawn with little to no figure.